/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
 *
 * This library is open source and may be redistributed and/or modified under
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSG_COORDINATESYSTEMNODE
#define OSG_COORDINATESYSTEMNODE 1

#include <osg/Group>
#include <osg/Matrixd>

namespace osg
{

const double WGS_84_RADIUS_EQUATOR = 6378137.0;
const double WGS_84_RADIUS_POLAR = 6356752.3142;

/** EllipsoidModel encapsulates the ellipsoid used to model astronomical bodies,
 * such as sun, planets, moon etc.
 * All distance quantities (i.e. heights + radius) are in meters,
 * and latitude and longitude are in radians.*/
class EllipsoidModel : public Object
{
    public:

        /** WGS_84 is a common representation of the earth's spheroid */
        EllipsoidModel(double radiusEquator = WGS_84_RADIUS_EQUATOR,
                       double radiusPolar = WGS_84_RADIUS_POLAR):
            _radiusEquator(radiusEquator),
            _radiusPolar(radiusPolar) { computeCoefficients(); }

        EllipsoidModel(const EllipsoidModel& et,const CopyOp& copyop=CopyOp::SHALLOW_COPY):
            Object(et,copyop),
            _radiusEquator(et._radiusEquator),
            _radiusPolar(et._radiusPolar) { computeCoefficients(); }

        META_Object(osg,EllipsoidModel);

        void setRadiusEquator(double radius) { _radiusEquator = radius; computeCoefficients(); }
        double getRadiusEquator() const { return _radiusEquator; }

        void setRadiusPolar(double radius) { _radiusPolar = radius; computeCoefficients(); }
        double getRadiusPolar() const { return _radiusPolar; }

        inline void convertLatLongHeightToXYZ(double latitude, double longitude, double height,
                                              double& X, double& Y, double& Z) const;

        inline void convertXYZToLatLongHeight(double X, double Y, double Z,
                                              double& latitude, double& longitude, double& height) const;

        inline void computeLocalToWorldTransformFromLatLongHeight(double latitude, double longitude, double height, osg::Matrixd& localToWorld) const;

        inline void computeLocalToWorldTransformFromXYZ(double X, double Y, double Z, osg::Matrixd& localToWorld) const;

        inline void computeCoordinateFrame(double latitude, double longitude, osg::Matrixd& localToWorld) const;

        inline osg::Vec3d computeLocalUpVector(double X, double Y, double Z) const;

        // Convenience method for determining if EllipsoidModel is a stock WGS84 ellipsoid
        inline bool isWGS84() const {return(_radiusEquator == WGS_84_RADIUS_EQUATOR && _radiusPolar == WGS_84_RADIUS_POLAR);}

        // Compares two EllipsoidModel by comparing critical internal values.
        // Ignores _eccentricitySquared since it's just a cached value derived from
        // the _radiusEquator and _radiusPolar members.
        friend bool operator == ( const EllipsoidModel & e1, const EllipsoidModel& e2) {return(e1._radiusEquator == e2._radiusEquator && e1._radiusPolar == e2._radiusPolar);}


    protected:

        void computeCoefficients()
        {
            double flattening = (_radiusEquator-_radiusPolar)/_radiusEquator;
            _eccentricitySquared = 2*flattening - flattening*flattening;
        }

        double _radiusEquator;
        double _radiusPolar;
        double _eccentricitySquared;

};

/** CoordinateFrame encapsulates the orientation of east, north and up.*/
typedef Matrixd CoordinateFrame;

/** CoordinateSystem encapsulate the coordinate system that is associated with objects in a scene.
    For an overview of common earth bases coordinate systems see http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys_f.html */
class OSG_EXPORT CoordinateSystemNode : public Group
{
    public:

        CoordinateSystemNode();

        CoordinateSystemNode(const std::string& format, const std::string& cs);

        /** Copy constructor using CopyOp to manage deep vs shallow copy.*/
        CoordinateSystemNode(const CoordinateSystemNode&,const osg::CopyOp& copyop=osg::CopyOp::SHALLOW_COPY);

        META_Node(osg,CoordinateSystemNode);


        /** Set the coordinate system node up by copying the format, coordinate system string, and ellipsoid model of another coordinate system node.*/
        void set(const CoordinateSystemNode& csn);

        /** Set the coordinate system format string. Typical values would be WKT, PROJ4, USGS etc.*/
        void setFormat(const std::string& format) { _format = format; }

        /** Get the coordinate system format string.*/
        const std::string& getFormat() const { return _format; }

        /** Set the CoordinateSystem reference string, should be stored in a form consistent with the Format.*/
        void setCoordinateSystem(const std::string& cs) { _cs = cs; }

        /** Get the CoordinateSystem reference string.*/
        const std::string& getCoordinateSystem() const { return _cs; }


        /** Set EllipsoidModel to describe the model used to map lat, long and height into geocentric XYZ and back. */
        void setEllipsoidModel(EllipsoidModel* ellipsode) { _ellipsoidModel = ellipsode; }

        /** Get the EllipsoidModel.*/
        EllipsoidModel* getEllipsoidModel() { return _ellipsoidModel.get(); }

        /** Get the const EllipsoidModel.*/
        const EllipsoidModel* getEllipsoidModel() const { return _ellipsoidModel.get(); }

        /** Compute the local coordinate frame for specified point.*/
        CoordinateFrame computeLocalCoordinateFrame(const Vec3d& position) const;

        /** Compute the local up-vector for specified point.*/
        osg::Vec3d computeLocalUpVector(const Vec3d& position) const;

    protected:

        virtual ~CoordinateSystemNode() {}

        std::string             _format;
        std::string             _cs;
        ref_ptr<EllipsoidModel> _ellipsoidModel;

};



////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// implement inline methods.
//
inline void EllipsoidModel::convertLatLongHeightToXYZ(double latitude, double longitude, double height,
                                      double& X, double& Y, double& Z) const
{
    // for details on maths see http://www.colorado.edu/geography/gcraft/notes/datum/gif/llhxyz.gif
    double sin_latitude = sin(latitude);
    double cos_latitude = cos(latitude);
    double N = _radiusEquator / sqrt( 1.0 - _eccentricitySquared*sin_latitude*sin_latitude);
    X = (N+height)*cos_latitude*cos(longitude);
    Y = (N+height)*cos_latitude*sin(longitude);
    Z = (N*(1-_eccentricitySquared)+height)*sin_latitude;
}


inline void EllipsoidModel::convertXYZToLatLongHeight(double X, double Y, double Z,
                                      double& latitude, double& longitude, double& height) const
{
    // handle polar and center-of-earth cases directly.
    if (X != 0.0)
        longitude = atan2(Y,X);
    else
    {
        if (Y > 0.0)
            longitude = PI_2;
        else if (Y < 0.0)
            longitude = -PI_2;
        else
        {
            // at pole or at center of the earth
            longitude = 0.0;
            if (Z > 0.0)
            { // north pole.
              latitude = PI_2;
              height = Z - _radiusPolar;
            }
            else if (Z < 0.0)
            { // south pole.
              latitude = -PI_2;
              height = -Z - _radiusPolar;
            }
            else
            { // center of earth.
              latitude = PI_2;
              height = -_radiusPolar;
            }
            return;
        }
    }
    
    // http://www.colorado.edu/geography/gcraft/notes/datum/gif/xyzllh.gif
    double p = sqrt(X*X + Y*Y);
    double theta = atan2(Z*_radiusEquator , (p*_radiusPolar));
    double eDashSquared = (_radiusEquator*_radiusEquator - _radiusPolar*_radiusPolar)/
                          (_radiusPolar*_radiusPolar);

    double sin_theta = sin(theta);
    double cos_theta = cos(theta);

    latitude = atan( (Z + eDashSquared*_radiusPolar*sin_theta*sin_theta*sin_theta) /
                     (p - _eccentricitySquared*_radiusEquator*cos_theta*cos_theta*cos_theta) );

    double sin_latitude = sin(latitude);
    double N = _radiusEquator / sqrt( 1.0 - _eccentricitySquared*sin_latitude*sin_latitude);

    height = p/cos(latitude) - N;
}

inline void EllipsoidModel::computeLocalToWorldTransformFromLatLongHeight(double latitude, double longitude, double height, osg::Matrixd& localToWorld) const
{
    double X, Y, Z;
    convertLatLongHeightToXYZ(latitude,longitude,height,X,Y,Z);

    localToWorld.makeTranslate(X,Y,Z);
    computeCoordinateFrame(latitude, longitude, localToWorld);
}

inline void EllipsoidModel::computeLocalToWorldTransformFromXYZ(double X, double Y, double Z, osg::Matrixd& localToWorld) const
{
    double  latitude, longitude, height;
    convertXYZToLatLongHeight(X,Y,Z,latitude,longitude,height);

    localToWorld.makeTranslate(X,Y,Z);
    computeCoordinateFrame(latitude, longitude, localToWorld);
}

inline void EllipsoidModel::computeCoordinateFrame(double latitude, double longitude, osg::Matrixd& localToWorld) const
{
    // Compute up vector
    osg::Vec3d    up      ( cos(longitude)*cos(latitude), sin(longitude)*cos(latitude), sin(latitude));

    // Compute east vector
    osg::Vec3d    east    (-sin(longitude), cos(longitude), 0);

    // Compute north vector = outer product up x east
    osg::Vec3d    north   = up ^ east;

    // set matrix
    localToWorld(0,0) = east[0];
    localToWorld(0,1) = east[1];
    localToWorld(0,2) = east[2];

    localToWorld(1,0) = north[0];
    localToWorld(1,1) = north[1];
    localToWorld(1,2) = north[2];

    localToWorld(2,0) = up[0];
    localToWorld(2,1) = up[1];
    localToWorld(2,2) = up[2];
}

inline osg::Vec3d EllipsoidModel::computeLocalUpVector(double X, double Y, double Z) const
{
    // Note latitude is angle between normal to ellipsoid surface and XY-plane
    double  latitude;
    double  longitude;
    double  altitude;
    convertXYZToLatLongHeight(X,Y,Z,latitude,longitude,altitude);

    // Compute up vector
    return osg::Vec3d(  cos(longitude) * cos(latitude),
                        sin(longitude) * cos(latitude),
                                         sin(latitude));
}

}
#endif
